The invention relates to devices for heating and/or air-conditioning the cabin of a motor vehicle.
More specifically, it relates to a mixing device for distributing, in variable proportions, a main air stream, particularly a stream of air flowing through an apparatus for heating and/or air-conditioning the cabin of a motor vehicle, between at least one hot air duct and at least one cold air duct.
It also relates to an apparatus for heating and/or air-conditioning particularly the cabin of a motor vehicle, comprising a casing delimiting a passage through which an air stream flows, this passage splitting into at least one hot air duct and at least one cold air duct.
Apparatuses for heating the cabin of a motor vehicle generally comprise a casing housing a blower for blowing an air stream through the casing and then distributing it into the cabin. A heater matrix, mounted as a bypass in a heating-air duct, allows the air to be heated before it is introduced into the cabin when the outside temperature is low, for example in the winter.
In order to allow the user to set the air temperature to suit him, the ventilation and heating apparatus is equipped with a device for mixing the air which allows the air stream to be distributed in variable proportions between the hot air duct and the cold air duct. The mixing device also allows the ventilation and heating apparatus to be operated in a xe2x80x9chotxe2x80x9d mode in which the cold air duct is entirely shut off so that all of the air passes through the heater matrix, and in a xe2x80x9ccoldxe2x80x9d mode in which the hot air duct is entirely shut off so that all of the air avoids the heater matrix. The mixing devices, in order to operate satisfactorily, need to meet a certain number of requirements.
First of all, the device needs to guarantee perfect sealing of the hot air and cold air ducts. In the cold mode, this involves avoiding drawing in hot air which would have the effect of heating up the air introduced into the cabin of the vehicle. In the hot mode, it involves avoiding drawing in any cold air so as to make best use of the heating capability of the matrix.
The device has to allow flexibility in the aerothermal optimization of the heating apparatus. What happens is that this apparatus has several outlets, particularly a deicing outlet, an outlet level with the dashboard and an outlet level with the feet of the driver and of the front-seat passenger. In better-equipped vehicles, it also comprises an outlet for the rear seats. The mixing device needs to be able to duct and to direct the air stream toward preferred points so as to distribute it correctly among the various outlets. It has also to allow the relative amount of hot air and of cold air to be adjusted precisely and to allow the hot and cold air streams to be mixed correctly.
Furthermore, the apparatus has to be as compact as possible in order to reduce its bulk. This is why there have been proposed (EP 0 958 951) mixing devices which use a shut-off plate arranged roughly at right angles to the air stream and sliding in slideways of the casing. Although it has the advantage of being compact, this device does have numerous disadvantages.
Sealing is afforded by a seal. The squashing of this seal generates a high friction force upon sliding of the plate in the slideway. This friction force entails a very high control force.
The use of a single shut-off element does not allow the amount of hot air and cold air to be adjusted in order to meet the required temperature conditions for intermediate positions of the control. Furthermore, given that the shut-off plate is in one piece, the regions of the matrix which lie behind it are not crossed by the air stream. This arrangement does not encourage good mixing of the air and aerothermal optimization of the heating apparatus.
The need to seal the device dictates the use of tight tolerances on the components and fits. These tolerances are difficult to achieve with the methods and materials generally used for producing heating and air-conditioning apparatuses. The cost of manufacture is therefore increased.
The subject of the present invention is a mixing device which solves these disadvantages. These objectives are achieved, according to the invention, through the fact that the mixing device comprises at least one panel comprising a perforation arranged in the hot air duct and a shut-off plate that can move between an open position in which it does not cover the perforation in the panel and a shut-off position in which it shuts off the perforation in the panel; at least one shutter for adjusting the passage cross section of the cold air duct that can move between an open position and a shut-off position, and a control mechanism for controlling, in synchronism, the movement of the shut-off plate and the movement of the shutter for adjusting the passage cross section of the cold air duct between their open position and their shut-off position.
These movements are synchronized in such a way that the passage cross section of the hot air duct increases when the passage cross section of the cold air duct decreases, and vice versa. Furthermore, the hot air duct is completely open when the cold air duct is completely closed, and vice versa.
Thus, the device comprises two independent adjusting elements, one for the hot air duct and the other for the cold air duct. The design of these elements and the logic dictating their movement make it possible for all the characteristics of the air mixing function to be satisfied in an optimum manner. It guarantees flexibility of adjustment of the quantity and of the localization of the air stream to be injected into the hot air duct and into the cold air duct. It makes it possible to produce highly permeable hot air and cold air circuits, that is to say circuits in which the pressure drop is low. The air stream from the blower, or from the evaporator if the heating apparatus has one, passes directly through the matrix without undergoing any significant change in direction.
This device guarantees perfect sealing of the cold air circuit. The latter is indeed shut off by a specific closure shutter, which can be adjusted independently of that of the hot air circuit. The movement of this shutter is preferably a rotational movement which, at the end of travel, generates a closure force in the direction of the shutter bearing surfaces.
As a preference, the panel comprises a number of perforations and the shut-off plate has a number of cutouts, the perforations in the panel and the cutouts in the shut-off plate being arranged with respect to one another in such a way that the hot air duct is shut off when the shut-off plate is in its shut-off position.
By virtue of this preferred feature, the air let into the hot air duct is distributed over the entire frontal surface of the matrix whereas, in the prior art mentioned earlier, there are regions of the matrix which the air stream does not reach.
Furthermore, the number, location, direction, shape and dimensions of the perforations in the panel and of the cutouts in the shut-off plate constitute parameters that can be altered in order to aerothermally optimize the apparatus. Furthermore, this arrangement allows the shut-off plate a small-amplitude excursion, less than half the height of the matrix. This small-amplitude excursion makes it easier for the mixing device to be incorporated into the low-volume apparatuses. It also makes it possible to observe a significant distance between the bottom of the shut-off plate and the end of the casing. This arrangement has the advantage of generating a large working volume for creating a tray for collecting condensate from the evaporator, to make it easier for this condensate to flow toward a discharge orifice and avoid placing the shut-off plate sealing system in contact with the condensate. This then gets around the problems of smell which may result from the presence of this condensate. There is an air passage possibility allowing good supply to the hot air and cold air circuits.
Also as a preference, the shut-off plate moves in a combined movement of translation and of rotation.
By virtue of this feature, the shut-off plate of the hot air duct circuit is sealed by bearing against a bearing surface. This bearing effect is generated by the rotational movement of the control member which, at the end of travel, transmits a closure force roughly in the direction of the bearing effect to be achieved. This mode of operation is opposed to the one in the device described previously which uses a sliding movement generating a force roughly parallel to the bearing effect and therefore not suited to guaranteeing a good seal.
Furthermore, the force to be employed in order to guarantee perfect sealing of the shut-off plate is not applied until the end of travel. It does not therefore affect the movement of the elements, which can move freely without significant force, during the most part of their movement.
Furthermore, the air pressure plays a part in pressing the shut-off plate against its bearing surface and encouraging sealing.
The position of the center and the length of the radius, and the angles subtended by the shut-off plate drive sector are parameters which further increase the flexibility in the aerothermal optimization of the mixing device. For example, a different position of the drive sector with respect to the shut-off plate may, for a given position of the temperature control, increase or decrease the amount of air injected into the lower part of the matrix.
Keeping the lateral faces of the panel away from the lateral edges of the shut-off plate may allow more air to be let in in addition to the air passing through the openings of the shut-off plate. This additional air stream may play a part in distributing the air even more uniformly over the entire frontal area of the matrix. This arrangement guarantees an optimum thermal matching coefficient.
Because the mixing device uses mainly transmissions of rotary movement, the contacts and friction between the parts are limited. That makes it possible to limit the control forces, the movement noises and the vibration of the parts, and the wear thereon. The reliability of the system is guaranteed by the possibility, when manufacturing the components, of keeping to low fit and movement tolerances.
Additional or optional features of the invention are listed below.
The heater matrix is roughly vertical; and then:
the device comprises a single cold air duct situated below the hot air duct;
the device comprises a single cold air duct situated above the hot air duct;
the device comprises a cold air duct situated below the hot air duct and a cold air duct situated above the hot air duct;
the device comprises a single cold air duct situated to the side of the hot air duct;
the device comprises two cold air ducts situated one to each side of the hot air duct;
the heater matrix is roughly horizontal; and in this case:
the device comprises a single cold air duct situated in front of the hot air duct;
the device comprises a single cold air duct situated behind the hot air duct;
the device comprises a cold air duct situated in front of the hot air duct and a cold air duct situated behind the hot air duct;
the device comprises a single cold air duct situated to the side of the hot air duct;
the device comprises two cold air ducts situated one to each side of the hot air duct;
the control mechanism comprises a control lever which controls the movement of the shut-off plate and the movement of the shutter for adjusting the passage cross section of the cold air duct;
the control lever controls the movement of the shut-off plate and/or the movement of the shutter for adjusting the passage cross section of the cold air duct via a link rod;
the control lever controls the movement of the shut-off plate and/or the movement of the shutter for adjusting the passage cross section of the cold air duct via a toothed sector;
the shut-off plate and/or the shutter for adjusting the passage cross section of the cold air duct are equipped with a balancing device;
the balancing device consists of a spring, a bob weight or scoops;
the shut-off plate and/or the shutter for adjusting the passage cross section of the cold air duct comprise air deflecting means such as bridging pieces or ribs to direct the hot air stream and/or the cold air stream toward chosen regions of a device for heating and/or air-conditioning the cabin of a motor vehicle;
the shut-off plate and/or the panel comprise sealing means for sealing the hot air duct when the shut-off plate is in the shut-off position;
the sealing means consist of flexible lips overmolded onto the panel and/or onto the shut-off plate;
the sealing means consist of a foam seal provided on the panel and/or on the shut-off plate;
the shut-off plate and/or the panel comprise means for attenuating the level of noise generated by their operation;
the means for attenuating the noise level consist of a profiling of the panel and/or of the shut-off plate;
the means for attenuating the noise level consist of inserts made of lightened material;
the means for attenuating the noise level consist of inserts covered with an insulating material;
the means for attenuating the noise level consist of a grating provided in the cutouts of the shut-off plate.
Furthermore, the invention relates to an apparatus for heating and/or air-conditioning particularly the cabin of a motor vehicle, and which comprises a mixing device according to the invention.
The device for mixing the air stream may be installed directly in the casing. Alternatively, the device for mixing the air stream may constitute an independent module attached into the casing.
Other feature and advantages of the present invention will become further apparent from reading the description which follows of some exemplary embodiments which are given by way of illustration with reference to the figures. In these figures:
FIG. 1 is a sectional overall view of a heating and air-conditioning apparatus comprising a mixing device according to the present invention;
FIG. 2 is a sectional part view of the apparatus depicted in FIG. 1, operating in cold mode;
FIG. 3 is a view similar to FIG. 2, the apparatus operating in an intermediate position;
FIG. 4 is a view similar to FIGS. 2 and 3, the heating and air-conditioning apparatus operating in hot mode;
FIGS. 5 to 8 depict various possible architectures of a heating and/or air-conditioning apparatus comprising a mixing device according to the present invention;
FIG. 9 depicts a heating and air-conditioning apparatus comprising a mixing device according to the invention constituting an independent module attached into the casing of the heating apparatus;
FIGS. 10 to 15 illustrate various embodiments of the mechanism for controlling the movements of the shut-off plate and of the shutter for adjusting the passage cross section of the cold air duct;
FIGS. 16 to 18 illustrate three possible alternative forms of embodiment of a mixing device according to the invention comprising means of balancing the control forces exerted on the shut-off plate and/or on the shutter for adjusting the passage cross section of the cold air duct;
FIGS. 19 to 21 illustrate three alternative forms of embodiment of means of sealing the panel and the shut-off plate against air;
FIG. 22 depicts an example of the layout of deflecting means on the shutter for adjusting the passage cross section of the cold air duct making it possible to aerothermally optimize the heating and/or air-conditioning apparatus; and
FIGS. 23 to 26 depict various arrangements making it possible to reduce the level of operating noise of the mixing device of the invention.